Thermostatic control switch



March 20, 1934. A BERTEA 1,951,920

THERMOSTATIC CONTROL SWITCH Filed Aug. 24, 1933 Patented Mar. 20, 1934 UNITED STATES THERMOSTATIC CON'IRL SWTCH Application August PA, 1933, Serial No. 686,633

13 Claims.

This invention relates to thermostatic control switches, and is more particularly concerned with means for producing a snap action in such switches.

One feature of the present invention is the employment of a permanent magnet for detaining a thermostatic switch blade against movement by thermostatic action until the energy stored up by the thermostatic action is suilicient to produce a rapid relative movement ci the switch members.

Another feature of the present invention is the provision of such a structure in which an assembly of magnet structure, contact devices, and insulating stop devices are incorporated.

A further object of the present invention is a simple, compact, and cheaply constructed thermostatic control switch assembly.

With these and other objects in view as will appear in the course of the following speciiication and claims, an illustrative form of constructing the device is shown on the accompanying drawing, in which:

Figure 1 is a plan view of the thermostatic control switch assembly.

Figure 2 is a corresponding view, but with one cover member removed.

Figure 3 is a transverse section substantially on line 3 3 of Figure 2.

Figure 4 is a longitudinal section substantially on line 4 4 of Figure 2.

Figure 5 is a plan view, on a much larger scale, of the assembly of the thermostatic bar and its adjustable support.

Figure 6 is a perspective view, substantially on the scale of Figure 2, showing the assembly of the magnet structure, contact, and insulating stop, with the conductors for the assembly.

Figure 7 is a perspective View, on a larger scale, of the magnet structure per se, with its associated parts.

In the drawing, the present invention is shown as applied to a small thermostatic control switch which is particularly valuable for use with a flexible heating pad. For such employment, the switch must be compact, free from projecting movable parts, and easily connected into the pad circuit. It will, of course, be understood that the principle of the invention is not limited solely to such employment.

The switch comprises a pair of cover members l0, 1l, which may be identical in shape and of insulating material. Each oi them has a cylindrical core portion 12 which together provide in effect a solid cylinder for reinforcing the cover (Cl. 20G- 139) members centrally of cavities 13 provided therein for the reception of the thermostat bar and its attached parts. A connecting bolt 14 passes axially through. the cylindrical cores and serves to hold the cover members together and the device in assembled condition. In the cover members, each is provided with a channel i5 by which the conductors may be brought to their respective terminals. The symmetricity of these conductor channels is apparent from Figures 1 and 2.

The cover members also have further cavities 16 for receiving the magnet structure as will be escibed hereinafter. Further, an aperture 17 provided in at least one of the cover members or gaining access to the thermostat bar structure or adjusting the same.

The thermostat bar structure comprises a bimetallic bar 18 which is illustrated as wound into spiral and as provided at its outer radially directed end with a clip piece 19 which preferably is of such magnetically-attractable material as iron or steel. The inner end of the spiral bimetallic bar is connected as by soldering or brazing at 2G to the hollow cylindrical hub 21 oi a toothed wheel 22. The internal diameter of the hub 2l establishes a close lit upon the cylindrical core portions l2, so that the contact of these parts tend frictionally to prevent relative motion thereof.

A pair of permanent magnets 25 are connected by rivets 25 at their poles. The two magnets 25 are spaced apart so that a contact disk 27 and an insulating stop disk 2S are held between the magnets, and project beyond the surfaces thereof (Fig. '7). A perforated soldering lug 29 contacting the dislr 27 is likewise received between the magnets at one pole end thereof and is joined to a conductor Se having insulation thereon and located in one of the conductor channels 15. Another conductor 3l is located in the other conductor channel l5, and at its end is connected a contact washer 32 having a central aperture which loosely fits the core portion l2 of one cover member, and being pressed upwardly by its own resiliency, and that oi the conductor 31, into maintained contact with the end surface of the hollow hub 21 (Fig. 1).

It will be noted that the thermostatic structure comprising the bimetallic bar with its clip, and the wheel 22 with its hub 21, may be made and moved as a separate sub-structure. The two magnets 25 may be identical, and are easily assembled with the contact and stop members and with the soldering clip 29 and conductor 3G as a further sub-assembly. The other conductor 31 and its washer 32 are likewise easily assembled. The two conductors may then be joined by twisting them together as illustrated, and the final assembly is then easily completed by inserting the magnet-washer-conductor assembly into the cavities of one cover member, forcing the hub 21 of a thermostatic bar structure down upon the core portion 12 of this cover member, iitting the other cover member in position, and securing the parts by a bolt 14.-. rlhe radially extending clip 19 of the bimetallic bar is merely seated between the contact 27 and the insulated stop 23. When the device has been assembled, it brought to predetermined temperature, and a small screw-driver or like instrument is introduced through aperture 1'? and engaged with the teeth of wheel 22 to adjust the device as desired. Further, it is obviously possible tc establish a substantially accurate adjustment, before placing the second cover member in position, by turning the toothed wheel 22 by the fingers. In this condition of the parts it will be noted (Fig. i) that the toothed wheel 22 extends above the rst cover member and is therefore easily accessible and it is possible to inspect the action ci the Contact and the clip during such a preliminary adjustment.

In operation, the s itch may be joined in series with the resistor wires in a heating pad, for example, and located at a point in the pad at which the temperature is to be regulated. While the device is cold, current flows through one conductor, say the conductor 30, to the soldering lug 29, contact 27, through the clip 19 which is then in engagement with contact 27, the bimetallic bar, hub 21, washer 32 and conductor 31. rlhis current energizes the heating resistors of the pad and t -e temperature rises therein. When the temperature has attained the point for which the device is set, the relative expansion of the parts of the bimetallic bar cause it tc change shape and thus tend to force the clip 19 relatively upwardly in Figure 2. The attraction of the magnets 25 for the clip and bar, however, prevent an immediate movement of the clip 19 away from contact 27. Ultimately, as the ten-- perature rises the thermostatic bar has stored up energy produced through the heat-induced change of form, a matter ci res iency in the bar, until finally the spring action is greater than the magnetic attraction and a movement of the clip 19 away from contact 27 starts. This spring action, however, decreases slowly with peripheral movements of the clip 19, while the magnetic attraction decreases, as is well known, substantially inversely as the square of the distance. Furthemore, the opposite pole immediately begins to exert attraction eiect. Thus, when once initiated, the movement of the clip 19 is very rapid, and a quick-snap breaking action occurs.

The circuit is thus interrupted and the pad tends to cool in the usual in cooling, the thermostatic bar 18 tends to return to its original form while cooled, so that there is a tendency toward peripheral movement of clip 19 in the opposite direction. This clip is at the moment engaged with the insulating stop 28, and is detained against movement by the attraction of the right hand pole, for example, in Figure '7. Ultimately, as the device cools, the energy stored in the thermostatic bar as a .resilient member overcomes the magnetic attraction and, in the same manner as before, a rapid movement of clip 19 into a new engagement with contact 2 occurs. The device thus has a quick-make and a quickbreak action, so that sparking and the attendant destruction of contact parts is largely avoided.

A further ieature in actual operation, is that the change of shape of the thermostatic spiral is accompanied usually by a slight radial movement, which is transmitted to the clip 19, and this clip tends to slide and/or roel; on the contact 27, so that the contact is not maintained only at a single point. During this sliding or rocking movement, the blade and clip are held against the contact 27 by the aforesaid magnetic attraction.

It is obvious that the invention is not limited solely to the especial form of construction shown, but that it may be employed within many ways of the scope oi the appended claims.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is:-

1. A thermostatic control switch comprising a magnet having spaced poles, a thermostatic bar including a movable end portion of magnetically attractable material located between said poles, conductor and contact means for establishing a circuit when said bar is in its closest proximity to one said pole, and an insulating piece for preventing contact of the bar with the other said pole for interrupting said circuit when the bar is at its closest proximity to said other pole, being actuated by change or" temperature conditions to move its end portion from one pole toward the other, said movement being delayed by the attraction of the magnet.

2. A. thermostatic control switch comprising a closure structure, a magnet supported by said closure structure and having spaced poles, a thermostatic bar including a movable end portion ci a magnetically attr ctable material located between said poles, and means for shifting the opposite end of said bar for adjusting the same including a movable member irictionally engaged with said structure and thereby held in adjusted position, said structure having a hole therein to provide access to said shifting means.

3. A thermostatic control switch comprising a closure structure having a cavity therein with a core portion, a magnet supported by said closure and having spaced poles, a rotatable member irictionally 'n-ounted on and held against movement by said core portion, a spiral thermostatic bar secured to said rotatable member at one end and having at its other and movable end a portion or" magnetically attractable material located between said poles, and conductor and contact means for establishing a circuit when said bar is in its closest proximity to one said pole and -for interrupting said circuit when the bar is at its closest proximity to the other said pole, said bar being actuated by change of temera-ture conditions to move its end portion from one pole toward the other, said movement being delayed by the attraction of the magnet.

Il. A switch as in claim in which the closure structure comprises identical parts each providing a part of the cavity and a part of the core portion, and in which said rotatable member comprises a toothed wheel and a hub, said hub being mounted on said core portion, and in which said closure structure has a hole through which access may be gained to the toothed wheel for moving the same.

5. n thermostatic control switch comprising a magnet in two parts, an insulating stop member located between the two parts at one pole of the magnet and projecting beyond the surface lill) of the said one pole, a thermostatic bar including a movable end portion of magnetically attractable material located between said poles, means for securing the magnet parts and stop member together, and conductor and contact means for establishing a circuit when said bar is in its closest proximity to the other` said pole and for interrupting said circuit when the bar is in engagement with said stop member, said bar being actuated by change of temperature conditions to move its end portion toward said stop member, said movement being delayed by the attraction of the magnet.

6. A thermostatic control switch comprising a magnet in two parts, a contact memb r located between said two parts at one pole of the magnet and extending beyond the surface of said one pole, a thermostatic bar including a movable end portion of magnetically attractable material located between said poles, means for preventing electric-al contact or said bar with the other said pole, and conductor and contact means cooperating with said contact rnd said bar for establishing a circuit when said bar is in its closest proximity to said one pole and for interrupting said circuit when the bar is at its closest proximity to the other said pole, said bar being actuated by change oi temperature conditions to move its end portion away fr in said contact, said movement being delayed by the attraction of the net.

'7. A thermostatic control switch comprising a closure structure having two communicating cavities therein, a magnet located in one cavity and having spaced poles located adjacent the other cavity, a thermostatic bar inclu.- g a movable end portion ci magnetically attractable material extending into said iirst cavity and located between said poles, means in the other said cavity for supporting the other end oi the thermostatic bar, means for preventing electrical contact of said bar with the other said pole, ccnductor and contact means for establishing a circuit when said bar is in its closest proximity to one said pole and for interrupting said circuit when the bar is at its closest proximity to the other said pole, said bar being actuated by change of temperature conditions to move its end portion from one pole toward the other, said movement being delayed by the attraction of the magnet.

8. A thermosta'ic control switch comprising a closure structure, a magnet and conductor assembly, and a thermostatic bar assembly; said magnet and conductor assembly comprising a permanent magnet and a Contact member' secured at one pole thereof and extending beyond the pcie surface, a conductor connected to contact member, an insulating stop member secured at the other pole of the magnet extending beyond the surface thereof, a contact washer and a second conductor connected to said washer and intertwined with said first conductor whereby the magnet and conductor assembly may be handled as a unit; said thermostatic bar assembly including a thermostatic having a movable end portion of magnetically attracts-,ble material located between said poles when the assemblies are in position on said closure structure.

9. A thermostatic control switch comprising a closure structure, a magnet oi two parts having spaced poles, an insulating stop member located between said parts at one pole and extending beyond the surface thereof, a contact member located between said parts at the other pole and extending beyond the surfaces thereof, rivets passing through said pole ends, said contact and said stop for securing the elements together, and a thermostatic bar including a movable end portion or" magnetically attractable mate `ial located between said poles and moved by change of temperature conditions from one said pole toward the other.

10. A thermostatic control switch comprising a closure structure, a magnet having spaced poles, a thermostatic bar assembly including a spiral portion and a radially extending movable end portion of magnetically attractable material located between said poles, a toothed wheel and a hub portion secured to said wheel and mounted on said closure structure, the inner end of said spiral bar being secured at the outer surface of said hub portion, said bar, wheel and hub portion forming a unit, and conductor and contact means for establishing a circuit when said bar is in its closest proximity to the one said pole and for interrupting said circuit when the bar is at its closest proximity to the other' said pole, said bar being actuated by change of temperature conditions to move its end portion from one pole toward the other, said movement being delayed by the attraction of the magnet.

il. A thermostatic control switch comprising a magnet having spaced poles, a magnetically attractable contact piece located between said poles, an insulating piece for preventing electrical contact or said contact piece with one said pole, a thermostatic device for producing a relative movement of said contact piece and magnet, and conductor neans electrically connected to said magnet and contact piece, said device being actuated by change oi temperature conditions to ei'- iect an electrical engagement of said contact piece with the other said pole or to break said contact, said movements being' delayed by the attraction oi the magnet.

l2. A thermostatic control switch comprising a magnet having spaced poles, a magnetically attractaole piece located between said poles, a thermostatic device tor producing a relative movement ci said attractable piece and magnet and a contact therebetween at one said pole, conductor means connected to said magnet and piece, and an insulating stop member for preventing contact or" said piece and the other said pole, said device being actuated by change of temperature conditions to produce said relative movement in a direction dependent upon the change of conditions whereby to make and breal said contact between said attractable piece and magnet at said one pole, said movements being delayed by the attraction or" the magnet.

i3. A thermostatic control switch comprising a closure structure having communicating cavities therein, a magnet supported in one said cavity by the walls thereof and having spaced poles adjacent the communication with another cavity, a spiral thermostatic bar having one end mounted in said other cavity and having the free end extending 'nto said one cavity and between said poles, said ree end including a magnetically a tractable porion movable back and forth between said poles, conductor and contact means connected with aid magnet and bar, said bar being actuated by hange ci temperature conditions to move its end portion from one pole toward the other, said movement being delayed by the attraction oi the magnet.

ALEXANDER BERTEA.- 

